"Rob [Marshall, the director] said he was in the Hamptons, and he saw her, and he said, 'It's top secret, but Emily Blunt's playing Mary Poppins,'" the actress said. "And she went, 'Oh, wonderful!'"

She added, "I felt like I wanted to cry. It was lovely to get her stamp of approval. That took the edge off it, for sure."

Yes, whew! Andrews' blessing is key, since, as Blunt noted, "It's such an important character in people's childhood."

"Mary Poppins Returns" will pick up 20 years after the original, in Depression era England, and will have a different take on the mystical English nanny, with the character more closely resembling the version in P.L. Travers's book. Which means, "She's a little meaner," Blunt teased.

Blunt will be joined by "Hamilton" creator/star Lin-Manuel Miranda and Meryl Streep in the movie, which is set for a December 2018 release.